In order to protect the body against risks such as fire, truly flame retardant fibers have been sought for a long time. In particular, a great deal of research and study has been directed at the development of fiber products capable of impeding the spread of fire or flame retardant products for the elderly and feeble suffering from difficulty to take refuge in the event of fire.
In addition, a variety of blackout curtains have been developed to prevent elevation of indoor temperature by blocking sunlight. A great deal of efforts have been made to develop blackout curtains made up of woven or knitted fabrics using fiber materials, blackout curtains fabricated from inorganic films and the like. Recently, since UV light has been discovered to be the primary cause of skin cancers, various methods have been proposed to block UV light.
There are various methods to prepare multi-functional products exerting functions such as flame retardancy, light shielding or the like, suited for the above-mentioned purposes. Firstly, mention may be made of a method for preparing a product using metal plates. In this case, the resulting products exhibit excellent performance such as complete incombustibility and perfect blockage of sunlight, but unfortunately may cause injury such as burns, due to an elevated temperature resulting from heat generated by energy of blocked sunlight.
As to another method, there is a preparation method using films made of organic materials. In the case of using organic films, it is possible to fabricate a larger variety of structures as compared to the use of metal plates, but there is a limit to the thickness of the prepared products. In addition, films made from such organic materials are unpleasant to the touch and exhibit poor drapeability.
Therefore, the present invention proposes a process for preparing a fiber product having excellent tactility and light shieldability and convenient handling ability using fibers simultaneously exhibiting flame retardancy and light shieldability.
Methods of imparting flame retardancy to the fiber may be broadly divided into a method involving flame retardancy processing and a method involving making fiber materials flame retardant, thereby imparting permanently flame retardant materials. The method using flame retardancy processing to impart flame retardancy has been conventionally performed on natural fibers such as cotton and is also employed in the production of flame retardant synthetic fibers. However, the method of imparting flame retardancy via post-processing presents problems associated with durability, and occurrence of environmental problems due to waste water generated during processing. As such, this method continues to be phased out.
In addition, as to the method involving rendering fiber materials permanently flame retardant, a method of imparting flame retardancy by copolymerization is primarily employed. For this purpose, reactive copolymerizable flame retardants are also variously commercialized.
Methods of forming flame retardant polyesters via copolymerization largely rely upon bromine (Br)-based flame retardants and phosphorus (P)-based flame retardants. As to patented inventions using bromine-based flame retardants, reference is made to Japanese Patent Publication Laid-open Nos. Sho 62-6912, 53-46398 and 51-28894. In this connection, bromine based compounds are susceptible to thermal degradation at high temperatures, and thus, a large quantity of flame retardants must be added in order to achieve effective flame retardancy. As a result, color and light fastness of the resulting polymeric material are deteriorated. In addition, due to the recent presentation of the possibility that bromine based flame retardants may give off carcinogenic substances such as dioxin and benzofuran, there is a movement towards regulation of brominated flame retardants, thereby actively facilitating substitution with the phosphorus based flame retardants.
As to patented inventions using phosphorus-based flame retardants, reference is made to U.S. Pat. Nos. 3,941,752, 5,899,428 and 5,180,793, and Japanese Patent Publication Laid-open No. Sho 50-56488. Reactive flame retardants disclosed in these patents have disadvantages such as deterioration of physical properties due to hydrolysis upon post-processing, in particular dyeing polyester fibers, because phosphorus atoms are bound to a main chain or backbone of the polymer.
On the other hand, flame retardant polyester fibers prepared using the above-mentioned patent methods lack UV stability and thus suffer from deterioration of flame retardancy/durability and physical properties of the fibers upon prolonged exposure to sunlight.
In this connection, Japanese Patent Publication Laid-open No. Hei 5-9536 has proposed a method of preparing fiber products for blocking sunlight by adding 2 to 39% by weight of inorganic fine particles having a particle size of not more than 5 μm in order to prepare a light shield for automobiles.
However, the light shield for automobiles prepared by such a method has no flame retardancy imparted by fiber per se. As such, the fiber must be subjected to post-processing if a flame retardant fiber is desired.